


Becoming The Experiment

by TellTaleKael



Series: Error’s Dolls [4]
Category: Undertale (Video Game)
Genre: Double Penetration, Double Penetration in One Hole, Error Actually Faces Consequences Of His Actions, Error Sans/Nightmare Sans/Cross Sans, Error/Nightmare/Cross - Freeform, Forced Sex, M/M, Nasty, Nightmare Gets Payback, Rape/Non-con Elements, Rough Sex, Sex Doll Magic, Sex Dolls
Language: English
Status: Completed
Published: 2021-02-19
Updated: 2021-02-19
Packaged: 2021-03-15 11:42:13
Rating: Explicit
Warnings: Rape/Non-Con
Chapters: 1
Words: 1,247
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29558583
Author URL: https://archiveofourown.org/users/TellTaleKael/pseuds/TellTaleKael
Summary: Error knew, the moment that Nightmare ripped a portal into the anti-void, that he was fucked.
Relationships: Sans/Sans (Undertale)
Series: Error’s Dolls [4]
Series URL: https://archiveofourown.org/series/2146278
Comments: 11
Kudos: 128





	Becoming The Experiment

**Author's Note:**

> Non-con ahead! Please take note of the tags and take care of yourself!

Error knew, the moment that Nightmare ripped a portal into the anti-void, that he was fucked. 

Tumbling out of his beanbag, he hit the ground running. But even with his strings, he didn’t make it far. One thick tentacle caught him around the waist, lifting him and smashing him down against the floor. Glitches exploded across his body, almost enough to send him crashing. He managed to stay conscious, but just barely, as Nightmare’s tentacles didn’t always register as the touch of another monster. 

Vision swimming, he peered around blearily as he was yanked forward, face to face with Nightmare. A cold grin greeted him. “Hello, Error. I think we need to talk.” Error nodded jerkily. “Good, good. I’m glad you agree.” He set Error back down on the beanbag, patting his skull just to watch him shiver at the touch. The portal behind him surged open again, and Cross came through, blade already summoned. “I hope you didn’t think I wouldn’t be able to sense your magic at play during that little stunt you pulled.”

Error sank further down into the beanbag, wishing it would just swallow him whole. “I d-dOn’t knOw AbOut thinK... so mUch aS hopE,” he muttered. Nightmare’s grin sharpened. 

“And we see where hope has gotten you.” Nightmare’s tentacles curled, all pointing directly at Error. “Now, why don’t you tell me how you did it?”

Reluctantly, Error obliged.

***

Nightmare was quiet for a moment after the explanation. Error could practically see the gears turning in his skull, always one to consider how to use a situation to his advantage. Error was just surprised that he wasn’t already in pieces. Nightmare couldn’t kill him, he always seemed to come back online no matter what, but he could certainly cause Error a world of pain. 

He made the mistake of looking up one to many times, towards the very dolls they were discussing. Nightmare noticed, jerking his skull, and Cross jumped. Error felt one of his strings sliced clean in two, and when Cross landed, he had a doll in hand. Passing it over to Nightmare, he looked somewhat flushed. Error’s body went cold when he realized exactly which doll Cross had fetched for Nightmare.

The little Error doll hung from Nightmare’s phalanges limply.

“I’m curious as to why you created a doll of yourself,” Nightmare began, stroking a single phalange over the dark skull. Error’s sockets fluttered at the touch, no glitches to be seen. “Unless you planned to give it to someone?” Nightmare’s smirk widened cruelly. “You long for someone’s touch. A touch that won’t make you crash.” He turned the doll over, grinding his thumb against the crotch harshly. Error whimpered. “We can make your dreams come true.”

He knew better than to try and run. His shorts were yanked down his legs, baring his lower half. The constant pressure against his crotch wouldn’t allow his magic to form, swirling shapeless and throbbing in his pelvis. He squirmed, trying to avoid Nightmare’s piercing gaze, and Cross’ look of awe. The bastard was flushed purple, inhaling deeply as if he could smell Error’s reluctant arousal. 

“Now, why don’t you form a nice hole for us?” Nightmare asked, pulling his thumb away. 

Error’s magic snapped in to place painfully fast. He was already dripping, pussy far more willing and eager than his mind was, almost as wet as he had been for Blue last time. Magic rose to his cheekbones, blue and yellow swirling in equal parts excitement and embarrassment. Two phalanges thrust into him, making him arch up with a startled cry. It was distressingly good, making him shiver and writhe. How long had it been since he had felt a touch like this?

The phalanges began to scissor, spreading Error out. He gripped the beanbag tightly, knuckles creaking from the force of his hold. It burned and ached so wonderfully. 

“Look at you.” The phalanges slid free, leaving Error gasping for breath he didn’t need. “So wet after just a few touches.” Nightmare chuckled, handing the doll over to Cross. “Use your intent to make him feel it,” he directed, before hooking his hands in Cross’ shorts and yanking them down. 

Cross’ cock was purple, darker at the weeping head. Error hadn’t been able to see it up close, so he hadn’t noticed the way it curved and throbbed when aroused. The leaking tip pressed against the doll, and Error felt it nestle between his folds. It seemed impossibly big.

“W-wAiT-“ he begged. Nightmare closed his hand around Cross’, shoving the doll down. Error’s entire body twitched and trembled as he was filled to the hilt, knees falling open wider. 

“Fuck, he’s tight,” Cross grit out, pulling Nightmare in for a kiss. He held still, probably adjusting to the sudden heat around his cock. Error didn’t know if he was glad for the change to adapt, or just ready for it to be over with. 

After a frankly filthy kiss, Cross and Nightmare began to move the doll simultaneously. Error rocked back with each sharp thrust, tearing into the beanbag with his phalanges. There was no mercy in the fast pace, and even without a touch to his clit, he approached his peak quickly. 

Just before he could spill over the edge, the thrusts stopped. Whining, he opened sockets he hadn’t even noticed were closed, looking at Cross. The soldier’s eyelights were only for Nightmare, however, who had pulled his own shorts down. Error’s sockets widened, and he choked out, “N-nO!” But his protest didn’t matter. Nightmare lined his teal cock up next to Cross’ and slid inside.

Stretched beyond belief, Error felt tears roll down his cheekbones. One cock would slide out while the other thrust in, never leaving him empty. Pleasure and pain melded together, mixing until they became one numbing feeling that wracked his entire body. He could faintly hear Nightmare murmuring to Cross, something soft and just for the soldier, but he was too far gone to make out the individual words. 

Someone’s phalange, he couldn’t tell who, slipped and brushed against Error’s clit, and he came with such force that he was surprised he didn’t crash anyway. He was floating, grounded only by the increasingly sloppy thrusts slamming into the back of his magic. The only warning he had was twin grunts, and then hot seed flooded into him, filling him up and leaking out of his entrance.

Both cocks slipped out, letting the magic pour freely out of him. The beanbag was sure to be ruined after this, torn and stained with teal and purple. Error forced his stiff phalanges to release, letting go of the torn fabric. He looked up as Nightmare approached, too exhausted to be afraid of what would happen next. 

A tentacle reached out, patting his skull again. The doll was placed beside him, absolutely dripping and soiled. “I don’t care what you do to anyone else, but don’t let me catch you using these on any of our people again,” he said lowly. “Don’t you touch ours again without permission, or I won’t go so easy on you next time.” He waited until Error nodded shakily before pulling away. “Good, I’m glad we understand each other.” 

A portal opened, and Cross walked through. Nightmare made to follow, but paused right before stepping through. “Oh, and Error? Make sure you make a doll using my brother’s code, won’t you? It could come in handy.”

With that, he left the anti-void behind. 


End file.
